This invention relates to breathing equipment, particularly resuscitators, and the invention is especially concerned with a novel form of valve mechanism for such equipment. Although the arrangement of the invention is adapted for use in breathing equipment of a variety of types, it is particularly adapted for use in resuscitators of the kind employing a manual squeeze bag providing for temporary breathing assistance to patients who have temporarily and at least partially lost capability of spontaneous breathing. Since the invention is particularly useful in resuscitators, it is described and illustrated herein as used in a resuscitator.
It is customary in equipment of this general kind to provide alternatively for delivering either air or oxygen to the patient, or any desired admixture of air and oxygen. It is also customary in equipment of this kind to employ a valve mechanism which is of the so-called "non-rebreathing" type, i.e. valve mechanism which assures that the gases which are exhaled from the patient's lungs will not be returned to his lungs upon the next succeeding inspiration.
The equipment of the present invention provides for the attainment of all of the above functions and, in addition, overcomes certain difficulties and disadvantages of prior known equipment of this kind, especially the problem explained herebelow which has been encountered in various prior forms of equipment.
Thus, with various of the prior art devices, at times when substantial amounts of oxygen (including 100% oxygen) are supplied to the patient from the customary pressurized source (for example the emergency oxygen tank carried by an ambulance or rescue vehicle), there has been a tendency for the valve mechanism "to lock" in a position maintaining the flow path open through the valve mechanism from the pressurized source to the patient's lungs, while closing off the expiration port. If this condition is not quickly observed or recognized by the operator of the equipment and if steps are not taken to interrupt this continuous delivery of pressurized oxygen to the patient's lungs, serious injury to the patient may result.
It is a major objective of the present invention to provide automatic valve mechanism, resulting in automatic oxygen "blow-by", which virtually eliminates the hazards heretofore incident to defective equipment and/or operation thereof in a manner not adequately compensating for tendency for the valve mechanism to "lock" in the undesirable position above referred to.
At the same time, the arrangement of the present invention retains all of the other desirable functions above referred to and affords various other advantages hereinafter brought out in the following description.